This invention relates to electric meters and more particularly to apparatus and circuits associated with a watt-hour meter for displaying data relating to electrical energy usage in the home of a consumer.
In view of the high cost of electrical energy, there is a need for letting a home consumer immediately know the cost of his current electrical bill as the electrical energy is being consumed and also the current cost per hour at which the energy is being consumed so that he can take steps to reduce the usage or otherwise conserve as he desires.
Prior art patents related to the subject matter of this invention include U.S. Pat. No. 4,204,115 which discloses an opto-sensor for sensing the rotation of a watt-hour meter calibrating disk having a single indicator mark on its periphery. Each time the indicator mark is sensed, a pulse is provided representative of the rate at which the power is being consumed. Later art, such as U.S. Pat. No. 4,399,510, discloses how such a pulse sensed each rotation of the warr-hour meter disk can be applied as a high frequency pulse on the household a.c. supply lines and sensed therefrom for feeding to a microprocessor for counting and conversion to cost parameters which are then projected and compared with a maximum budgeted amount for monitoring purposes.
It should be particularly noted, however, that these prior art patents do not provide for displaying data which lets a consumer immediately know, as the energy is being used, not only what the cost is for the current billing period but also the current cost per hour of the energy being consumed. Moreover, these prior art patents do not provide a simple and inexpensive means for displaying data which lets a consumer known how much it costs to dry a load of clothes, for example, or how much electrical energy is being used each evening, say, from 6 p.m. till bedtime. The ability to display such data is important inasmuch as it enables a consumer to determine if he is conserving.
Thus, in a system wherein a single pulse is provided each revolution of a watt-hour meter disk, and especially when the power is being consumed at a relatively low rate, it takes such a long time before an incremental change in power, as represented by the pulse, is sensed, that it is impossible for the consumer to be kept currently informed as to what the situation is as far as power usage is concerned.